US 2003/0036700 A1 discloses a system for obtaining an image of a body part within a body, wherein a radiotracer including Indium-III has been administered intravenously to the body such that the radiotracer accumulates preferentially in the body part. The system comprises a first gamma ray sensor configured to detect prompt gamma rays emitted by Indium-III, wherein the first gamma ray sensor is positioned external to the body, and a second gamma ray sensor configured to detect prompt gamma rays emitted by Indium-III, wherein the second gamma ray sensor is positioned either internally within the body or within a body orifice or body cavity.
WO 2007/082126 A2 discloses a time-of-flight imaging apparatus, wherein the apparatus comprises a) a window generator that generates a dynamic acceptance window based on a profile of a subject and an intrinsic resolution of the imaging system, b) a plurality of radiation detectors that generate signals indicative of each radiation event detection, and c) a line of response processor that identifies a spatial line of response connecting a pair of radiation detections corresponding to a common radiation event. The apparatus further comprises d) a windowing component that filters the radiation event detections by using the dynamic acceptance window and e) a reconstruction engine that reconstructs images based on the remaining non-filtered radiation event detections.
A PET system may comprise an outer detector ring and a PET endoprobe to be introduced into a person. The outer detector ring and the PET endoprobe are adapted to detect gamma ray photons generated within the person, when corresponding radioisotopes decay by positron emission. When a positron is emitted by a nucleus, it almost instantly finds an electron, and the pair annihilates, converting all the mass energy of the two particles into gamma ray photons travelling in opposite directions. A substantially simultaneous detection of these gamma ray photons in two detector elements places the radiation source, i.e. the radioisotopes, on a line connecting the two detector elements, wherein two gamma ray photons are regarded as being simultaneously detected, if a difference between the respective detection times is smaller than a preset threshold. A lot of different coincident gamma ray photons and thus corresponding lines, on which the radiation source is arranged, are detected, wherein these lines can be used for reconstructing a PET image. However, the quality of the PET image may be relatively low in comparison to, for instance, a magnetic resonance (MR) image or a computed tomography (CT) image.